The dynamics of natural transmission of cutaneous and mucocutaneous leishmaniasis will be studied in different climatic and ecological zones of Costa Rica, where the disease occurs endemically and shows diverse epidemiological characteristics. This study will include detailed investigation of the indigenous opulation, the sandfly fauna, and the animal reservoirs, and the identification of hemoflagellates isolated from them. The results obtaind in the different areas will be compared in a search for distinctive patterns related to the reservoirs involved, the sandfly species present, their seasonal variations and their host preferences. The protective effect of immunization with killed or live vaccines and other types of antigens with or without adjuvants will be studied in experimental animals. The relationship of hypersensitivity tests to length of infection and to the immunity mechanisms will be investigated both in experimental animals and in humans. Also, well known methods will be used to produce immunological imbalance in the experimental models to further classify the host response. A search will be made for the existence of visceral leishmaniasis in Costa Rica.